Question

In Section \(1.1\) of the text, the concept of a chemical reaction was introduced with the example of the decomposition of water, represented as follows: Use ideas from Dalton's atomic theory to explain how the above representation illustrates the law of conservation of mass.

Short answer

The decomposition of water, represented by the chemical equation \(2H_2O \rightarrow 2H_2 + O_2\), demonstrates the law of conservation of mass according to Dalton's atomic theory. Before the reaction, there are 2 water molecules with 4 hydrogen atoms and 2 oxygen atoms. After the reaction, there are 2 hydrogen gas molecules with 4 hydrogen atoms and 1 oxygen gas molecule with 2 oxygen atoms. The number of atoms of each element remains the same before and after the reaction, showing that the mass is conserved. This is consistent with Dalton's atomic theory, proving the law of conservation of mass.

Step-by-step solution

Understand Dalton's Atomic Theory

Dalton's atomic theory has several key points, including: 1. All matter is made of atoms, which are indivisible and indestructible particles. 2. All atoms of a given element are identical in mass and properties. 3. Compounds are formed by the combination of two or more different kinds of atoms. 4. A chemical reaction is a rearrangement of atoms.

Write the chemical equation for the decomposition of water

In the decomposition of water, water molecules break down into hydrogen gas and oxygen gas. This can be represented by the following chemical equation: \[2H_2O \rightarrow 2H_2 + O_2\]

Analyze the chemical equation

According to the given equation: - Two water molecules (each containing two hydrogen atoms and one oxygen atom) break down. - As a result, two hydrogen gas molecules (each containing two hydrogen atoms) and one oxygen gas molecule (containing two oxygen atoms) are formed.

Apply the law of conservation of mass

Now let's analyze how the decomposition of water illustrates the law of conservation of mass. The law of conservation of mass states that the total mass of all substances involved in a chemical reaction remains constant before and after the reaction. In the given chemical equation: Before the reaction, we have: - 2 water molecules (4 hydrogen atoms and 2 oxygen atoms) After the reaction, we have: - 2 hydrogen gas molecules (4 hydrogen atoms) and 1 oxygen gas molecule (2 oxygen atoms)

Conclusion

As we can see, the number of atoms of each element remains the same before and after the reaction, illustrating the law of conservation of mass, which is consistent with Dalton's atomic theory. In this case, the total mass before the reaction is equal to the total mass after the reaction, proving the law of conservation of mass.

Key concepts

Dalton's Atomic Theory

Dalton's Atomic Theory is a cornerstone in the world of chemistry. It provides a simple yet powerful explanation for how substances are constructed and behave during chemical reactions. One of the essential ideas proposed by John Dalton is that all matter is composed of atoms, the smallest unit of an element that maintains the properties of that element. Dalton suggested that these atoms are indivisible and cannot be destroyed in chemical processes.

According to Dalton's theory, atoms of the same element have identical masses and properties. This assumption was crucial for explaining why substances react in certain ways. When it comes to chemical compounds, Dalton stated that they are formed through the combination of two or more different types of atoms, a concept that is still valid today. Finally, Dalton's theory posits that chemical reactions involve only the rearrangement of atoms, never their creation or destruction.

These basic principles laid down by Dalton help us comprehend the behavior of elements during reactions with the preservation of mass, a concept directly tied to the law of conservation of mass.

Chemical Reaction

A chemical reaction is a process in which substances, known as reactants, are transformed into different substances called products. This transformation occurs through the breaking and forming of chemical bonds, leading to a rearrangement of atoms.

During a chemical reaction, the initial substances undergo changes in their chemical structure to form new substances. It's important to note that while the composition of substances changes, the total number of atoms remains the same throughout the process. This is because atoms simply shift positions, instead of being created or destroyed.

An ideal example of a chemical reaction is the decomposition of water, where water molecules break down into hydrogen gas and oxygen gas. Through such reactions, we observe the fundamental laws of chemistry, like the law of conservation of mass, where the mass of the reactants equals the mass of the products.

Decomposition of Water

The decomposition of water is a specific kind of chemical reaction where water ( \(H_2O\) ) is broken down into its elemental components, hydrogen ( \(H_2\) ) and oxygen ( \(O_2\) ). This process can be represented by the chemical equation: \[2H_2O \rightarrow 2H_2 + O_2\]

In this reaction, each water molecule splits into two atoms of hydrogen and one atom of oxygen. When you look closely at the equation, you'll notice that two water molecules decompose to form two molecules of hydrogen gas and one molecule of oxygen gas.

This process exemplifies the law of conservation of mass. Before and after the reaction, the same number and type of atoms are present. Therefore, the mass remains unchanged. By understanding the decomposition of water, we gain insight into how chemical reactions conserve the total mass, honoring Dalton’s atomic theory by merely rearranging atoms rather than creating or destroying them.